Breast cancer is a major cause of death of American women. However, there is little information on biochemical and immunological events that occur in human breast tissue during the neoplastic process. Our past studies have shown that sera from women with breast cancer have antibodies reactive with a human breast tumor cell line, BOT-2 cells. Our recent studies show that the proteins isolated from BOT-2 cells are reactive with sera from breast cancer patients. Preliminary studies indicate that the proteins isolated from BOT-2 cells are quite similar, biochemically, to proteins isolated by others from whole human breast tumor tissue. The objectives in this proposal are to isolate and purify the proteins from BOT-2 cells using standard chromatographic and electrophoretic methods. The data will indicate the biochemical nature of human breast tumor proteins and may be quite useful in future serodiagnostic, therapeutic, and immunologic studies of human breast cancer.